Process of rendering iron and steel nonoxidizable and articles produced thereby



Patented Feb. 15, 1927.

UNITED STATES PATENT OFFICE.

EDWARD G. CAUGHEY, ,OF SEWIGKLEY PENNSYLVANIA, ASSIGNOR-TO EDGEWATER STEEL COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIL rnocnss F RENDERING IRON AND STEEL NONQXIDIZABLE AND ARTICLES rrtonncnn THEREBY.

\ No Drawing.

This invention relates in general to the protection of. iron or steel from oxidation and particularly where such steelor 'iron is subjected to high temperatures as in annealing boxes, carbonizing cases, furnace parts, etc: Annealing boxes may be taken as an example of an excellent use of the invention. Such boxes are subjected to temperatures as high as 2000 Fahrenheit and at this and intervening temperatures steel oxidizes very rapidly, as is readily observable upon comparing the weight of an annealing box after a considerable number of uses with its initial weight, until finally the walls become so thin that they must be discarded. H

Another excellent use for the invention is in pots for hardening gears. and .other such articles. These pots, as ordinarily constructed of cast steel, last about 630 total the provision of a material which will not.

oxidize nor absorb the carbonizing elements in which the steel to be carbonized has been packed at this high temperature and which accordingly may be used indefinitely without permanent deterioration. In connection with the carboniaing pots it may be men-' tioned that my material shows no scaling after the first treatment, no loss of weight after about a 1050 hour test givenit. In deed after the prolonged test given it the material could not be said to have changed color. I I The invention relates also to the process of rendering ironor steel non-oxidizable at high temperatures, and also to a process for maintaining such material in the original structural condition. -I have found that material embodying m invention, if left in the ordinary room or at atmospheric temperatures, gradually sufi'ers structural deterioration and as a part of my present inven- Application filed January 26, 1922. Serial No. 532,025.

tion I havediscovered a process" for correcting such deterioration so that properly handled. the material may maintain its desirable qualities indefinitely.

The process of treating the steel ,to form the material embodying my invention consists essentially of incorporating in it a quantity of aluminum designed to produce a resultant mixture. best adapted to resist oxidation and the absorption of carbonizing and other materials at high temperatures.

-I dissolve an amount of aluminum in the steel, determined by the temperature at which protection against oxidation is most des red, 1. e. calculated to present maxlmum' resistance to oxidat on at the highest temperature to which the material is ordinarily subjected. I have found by experiment that in the case of an annealing box to resist.

high temperatures andmade from low car-- bon steel, material with approximately12% to 15% of aluminum in the steel gives satisfactory results. The two -materials are melted and united in moltencondition. It is believed that the aluminum cornbines with j the iron to form an iron aluminum compound and that after the metal has solidified this iron aluminum compound is dissolved in the remainder of the metal as a solid solvent. I have found that this material cast into annealing boxes, carboniz ing pots, etc., will permanently resist oxidation at the high temperatures such articles are ordinarily subjected to. I have found, howeverythat this material upon being allowed to stand at atmospheric temperatures undergoes a structural change and deteriorates and my researches indicate that the-steel, being saturated at higher temperatures with the aluminum compound, is super-saturated at atmospheric temperatures and gradually and slowly the aluminum compound passes out of solution collecting between the grains and along their cleavage plan'es, thus weakeningtheir natural bond. This may be overcome and corrected by periodic or occasional heating of the material to a temperature not ex'-' ceeding that at which the annealing'boxes,

carbonizing pots, or other articles are designed to withstand in service. This may be accomplished by especial heating or as an incident to the use of the article made of the material. I have discovered that theoriginal condition is reestablished and that the aluminum or the aluminum iron compound passes back into solution, thus restoring the original physical properties of the material.

W'hile in the claims the expression iron is used it will be understood that by this term it is intended to include steel aswell. It is further stated that this material is very hard and that the invention contemplates the use of a lower percentage of aluminum with resulting lower percentage of aluminum compound in solution in order to provide a material more readily forged and worked. It will also be understood that in so far as the prevention of absorption of carbon is concerned in carbonizing pots and the like where the invention is employed, my present intention is that the absorption is prevented by the saturation at the working temperature of theiron by the iron alumipasses into of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

1 claim:

1. A process of rendering iron non-oxidizable or resistant to oxidation at high temperatures, which includes, incorporating in the iron as a solid solvent a quantity of aluminum to form a saturated solution in said solvent at the temperature at which it is particularly desired to prevent oxidation.

process of rendering iron non-oxidizable or resistant to oxidation at high temperatures, which includes, incorporating in the iron as a solid solvent :1. quantity of aluminum to form a saturated solution in said solvent at the temperature at'which it is particularly desired to prevent oxidation and bringing said iron to said temperature upon occasion to redissolve any aluminum compound separated out at lower intervening temperatures.

3. A process of rendering iron non-oxidizable or resistant to oxidation at high teming temperature to which the treated iron' is subjected in service.

5. A metal article adapted to be subjected to high temperatures in service and formed of a material non-oxidizable by such temperatures, comprising iron as a solvent in which has been dissolved a quantity of aluminum, approximately in amount appro-' priate to form a saturated solution of aluminum compound in the iron at the temperature at which oxidation is to be prevented.

6. A metal article adapted to be subjected to high temperatures in service and formed of a material non-oxidizable by such temperatures, comprising iron with a quantity of aluminumdissolved in the iron as a solid solvent, in amount appropriate to form a saturated solution at the highest working temperatures to which said material is to be subjected. r

7. A metal article adapted to be subjected to high temperatures inservice and formed of a material non-oxidizable by such temperatures, comprising a mixture of iron and aluminum in amount appropriate to prevent oxidation, the relation of said iron and said aluminum in saidmixture being such that structural deterioration results from protracted interrupted subjection of the mixture to atmospheric temperature, and reestablishment of the original structure ob.- tainable by heating of said iron to a higher temperature.

EDWARD G. osinsnnv.

too 

